NOAA Teacher at Sea
Aboard NOAA Ship Pisces
May 1-May 12, 2017
Mission: SEAMAP Reef Fish Survey
Geographic Area of Cruise: Gulf of Mexico
Date: May 8, 2017
Weather Data from the Bridge
Latitude: 2755.757 N, Longitude: 9200.0239 W
Wind Speed: 14.21 knots, Barometric Pressure: 1015.3 hPa
Air Temperature: 24.56 C, Water Temperature: 24.4 C
Salinity: 36.37 PSU, Conditions: 50% cloud cover, light wind, seas 2-4 feet
Science and Technology Log
The CTD (conductivity, temperature, depth) array is another important tool. It goes down at each station, which means data is captured ten-twelve times a day. It drops 50 m/min so it only takes minutes to reach the bottom where other winch/device systems can take an hour to do the same. This array scans eight times per second for the following environmental factors:
- Depth (m)
- Conductivity (converts to salinity in ppt)
- Temperature (C)
- Dissolved oxygen (mg/mL)
- Transmissivity (%)
- Fluorescence (mg/m^3)
- Descent rate (m/sec)
- Sound velocity (m/sec)
- Density (kg/m^3)
There are two sensors for most readings and the difference between them is shown in real time and recorded. For example, the dissolved oxygen sensor is most apt to have calibration issues. If the two sensors are off each other by 0.1 mg/L then something needs to be done.
Software programs filter the data to cut out superfluous numbers such as when the CTD is acclimating in the water for three minutes prior to diving. Another program aligns the readings when the water is working through the sensors. Since a portion of water will reach one sensor first, then another, then another, and so on, the data from each exact portion of water is aligned with each environmental factor. There are many other sophisticated software programs that clean up the data for use besides these two.
These readings are uploaded to the Navy every twelve hours, which provides almost real-time data of the Gulf. The military uses this environmental data to determine how sound will travel through sound channels by locating thermoclines as well as identifying submarines. NOAA describes a thermocline as, “the transition layer between warmer mixed water at the ocean’s surface and cooler deep water below.” Sound channels are how whales are able to communicate over long distances.
The transmissometer measures the optical properties of the water, which allows scientists to track particulates in the water. Many of these are clay particles suspended in the water column. Atmospheric scientists are interested in particulates in the air and measure 400 m. In the water, 0.5 m is recorded since too many particulate affects visibility very quickly. This affects the cameras since light reflecting off the clay can further reduce visibility.
Fluorescence allows scientists to measure chlorophyll A in the water. The chlorophyll molecule is what absorbs energy in photosynthetic plants, algae, and bacteria. Therefore, it is an indicator of the concentration of organisms that make up the base of food chains. In an ecosystem, it’s all about the little things! Oxygen, salinity, clay particles, photosynthetic organisms, and more (most we can not actually see), create a foundation that affects the fish we catch more than those fish affect the little things.
The relationship between abiotic (nonliving) and biotic (living) factors is fascinating. Oxygen is a great example. When nitrates and phosphates wash down the Mississippi River from the breadbasket of America, it flows into the Gulf of Mexico. These nutrients can make algae go crazy and lead to algae blooms. The algae then use up the oxygen, creating dead zones. Fish can move higher up the water column or away from the area, but organisms fixed to the substrate (of which there are many in a reef system) can not. Over time, too many algae blooms can affect the productivity of an area.
Salt domes were created millions of years ago when an ancient sea dried up prior to reflooding into what we have today. Some salt domes melted and pressurized into super saline water, which sinks and pools. These areas create unique microclimates suitable to species like some mussels. A microclimate is a small or restricted area with a climate unique to what surrounds it.
Another great example is how geology affects biology. Some of these salt domes collapsed leaving granite spires 30-35 meters tall and 10 meters across. These solid substrates create a magical biological trickle down effect. The algae and coral attach to the hard rock, and soon bigger and bigger organisms populate this microclimate. Similar microclimates are created in the Gulf of Mexico from oil rigs and other hard surfaces humans add to the water.
Jillian’s net also takes a ride with the CTD. She is a PhD student at Texas A&M University studying the abundance and distribution of zooplankton in the northern Gulf of Mexico because it is the primary food source of some commercially important larval fish species. Her net is sized to capture the hundreds of different zooplankton species that may be populating the area. The term zooplankton comes from the Greek zoo (animal) and planktos (wanderer/drifter). Many are microscopic, but Jillian’s samples reveal some translucent critters you can see with the naked eye. Her work and the work of others like her ensures we will have a deeper understanding of the ocean.
Prior to this I had never been to the Gulf of Mexico other than on a cruise ship (not exactly the place to learn a lot of science). It has been unexpected to see differences and parallels between the Gulf of Mexico and Gulf of Maine, which I am more familiar. NOAA scientist, John, described the Gulf to me as, “a big bathtub.” In both, the geology of the area, which was formed millions of years ago, affects that way these ecosystems run.
Quote of the Day:
Jillian: “Joey, are we fishing at this station?”
Joey: “I dunno. I haven’t had my coffee yet.”
Jillian: “It’s 3:30 in the afternoon!”
Did You Know?
Zooplankton in the Gulf of Mexico are smaller than zooplankton in the Gulf of Maine. Larger species are found in colder water.